1. Field of the Invention
The invention relates to tool box or tool case, in particular, for receiving portable working devices. The tool box or tool case can be stacked vertically and comprises a shell-shaped bottom part with an upwardly facing opening as well as a cover for closing the opening.
2. Description of the Related Art
For storing and transporting portable working devices, such as hand-held electric tools, drills or the like as well as for heavy tools in general, a plurality of tool boxes are known which must fulfill several, partially contradictory requirements. For example, for storing new devices, the tool boxes enclosing them must be stackable easily and the storage space occupied by them should be as small as possible. This results in requirements demanding a stacking height as high as possible in connection with a compact configuration. Because of the resulting high mechanical loads acting on the tool box at the bottom of the stack, the tool boxes must be configured to be correspondingly strong. At the same time, a minimal weight of the tool box itself is desirable, for example, in order to enable easy handling of the tool box at a construction site.
European patent 0 555 533 describes a stackable tool box or tool case for transportable machine tools which comprises a box or shell-shaped bottom part and a cover. Stacking several of these boxes is possible in that the bottom part of the box on top is placed onto the cover of the box arranged underneath, respectively. The cover of the box in the lower position, respectively, is secured between the bottom part of the lower box and the lower part of the box placed directly on top. In the stacked condition, such a cover must therefore be able to support the weight of one or several such stacked boxes and their contents. The cover is thus significantly stressed which can result in damage of the cover itself or of its hinges and closures. Connecting means are provided which enable a detachable connection between the bottom parts of two boxes that are directly stacked on top, respectively, and the formation of a contiguous transport unit comprised of several boxes. This supposedly provides the possibility of lifting the stack of boxes by engaging the uppermost box wherein the lower boxes are suspended from the top one, respectively, by means of the connecting means. For a tight connection which prevents or inhibits sliding of the boxes relative to one another a certain pretensioning force of the connecting means is required.